My starter was starting to occasionally spin the bendix gear, especially when cold. Today, the car wouldn't start. After pulling the negative terminal clamp, cleaning a bit (soda to remove the buildup, and scraping), and putting it back on, I was able to start it up and drive home.
Battery voltage, 12.59 volts, reasonably nominal.
Problem - After pulling clamps, cleaning (vinegar and wire brush), and remounting - everything _seemed_ right, until I turned the key. Click.
Voltage on battery sagging like crazy. Started rapping the starter, with my wife turning the key, and it started.
Problem - with low RPM, the voltage of the alternator .... wasn't there. The battery basically just showed the battery voltage. Rev the engine, and the voltage went up to 14.1, but you had to hold up the RPMs. Let it idle, and the voltage drops to next to nothing.
Classic signs of alternator failure. (I doubt any of my grounds are bad; no other signs)
So I just picked up a replacement starter AND alternator. Not looking forward to it, but I have to replace them ASAP. Luckily, I can use my wife's car for a couple of days, but I'm going to try to replace them tomorrow. It's a bit dark to do it right now unless desperate.
Edit - At 178k miles, I'm not surprised at the starter, but I am surprised about the alternator.